Multi-lumen catheters are “suitable”, based on conventional wisdom and usage, for use in conjunction with hemodialysis applications. Having two (2) or more lumens means two (2) or more separate fluid flow passages. For hemodialysis applications, one (1) lumen handles the flow of blood being removed for processing by a dialysis machine and the other lumen handles the blood being returned to the patient. The use of a multi-lumen catheter, normally a dual lumen catheter, allows the contaminated blood (“bad” blood) and the cleansed blood (“good” blood) to be kept separate as part of an effective dialysis procedure.
Current hemodialysis catheters are used to filter blood in the superior vena cava (SVC). When using a two-lumen hemodialysis catheter, the arterial lumen is used to aspirate blood which is routed to the dialysis machine for cleansing. The venous lumen is used to eject the filtered blood (good blood) into the SVC and then to the heart and lungs, and to the rest of the body of the patient.
Traditionally, the venous (out-flow) lumen is always the distal lumen and the arterial (in-flow) lumen is always the proximal lumen. This is done to prevent recirculation, where previously filtered and newly ejected blood is sucked back in and re-filtered by the dialysis machine. Depending on the catheter tip design and placement, the proximal arterial opening can suck the SVC wall next to it, occluding the opening, lowering the flow rate, and preventing dialysis from taking place. Various prior art hemodialysis catheters have sideports to allow the in-flow of blood from multiple openings. However, this arrangement prevents the use of heparin (or other anti-coagulants) from being used as a “lock”. With these prior art constructions, heparin can leak out of the sideports leaving anything distal to the sideport unprotected. As used herein, a heparin “lock” is when the catheter is flushed with heparin and then clamped off between uses, so that the normal inside volume of the catheter is occupied thus preventing thrombus from forming. Various (prior art) medical journal articles point to hemodialysis sideports being a cause of thrombosis and fibrin sheath formation, thus lowering flow rates and making a catheter essentially non-functional.
A solution to one (1) or more of these prior art issues is provided by the exemplary embodiment of the present disclosure. A curved tip hemodialysis catheter is disclosed wherein the curved construction functions, in part, as a type of reinforcement against any appreciable movement of the SVC wall which might be sufficient to occlude a flow opening of the catheter. This issue has been mentioned above and is discussed in the context of the proximal arterial opening where the SVC wall can be sucked into an occluding position over at least a part or portion of that opening.
The use herein of “curved tip” refers to the distal portion of the catheter and not merely to the distal end. The “tip” refers to that distal portion or length which is sufficient to form a curved, part-circular shape, as described in greater detail herein.
The size, shape and material resiliency of the curved tip portion provides support against the inner surface of the SVC wall. This curved tip portion functions to physically spread apart the SVC, similar in this regard to a vena cava filter. The level or degree of physical support or physical reinforcement against the SVC wall which is provided by the curved tip portion of the disclosed catheter prevents the SVC vein wall from being sucked around the flow opening of the arterial (in-flow) lumen of the catheter. The exemplary embodiment negates any “need” for possible corrective measures such as the addition of sideports and in so doing eliminates the risk of end hole thrombus. One (1) result expected from the exemplary embodiment, as contrasted to prior art structures which have the discussed “issues”, is an increased flow rate and a decrease in the total time to dialyze a patient.
One (1) consequence of shaping a hemodialysis catheter with a curved tip is to reverse or switch the traditional functionality of the two (2) lumens of the catheter. Traditionally, the proximal lumen is the arterial lumen for in-flow and the distal lumen is the venous lumen for out-flow. While the two (2) lumens of the catheter essentially run side-by-side, the use of “proximal” and “distal” refers to the relative locations of the defined flow openings for each of those two (2) lumens. In the exemplary embodiment, considering simply the elongated form of the catheter prior to being formed with a curved tip, these two (2) flow openings are reversed. In this regard, it will be seen that in the exemplary embodiment the flow opening which is proximal corresponds to the venous lumen and the flow opening which is distal corresponds with the arterial lumen. It will also be seen that surrounding the flow opening of the arterial lumen, there are no sideports.
The addition of a tip curvature of at least approximately 180 degrees provides a structure wherein the flow openings of the two (2) lumens are separated further. As disclosed herein, relative to the exemplary embodiment, the venous lumen and its flow opening point in a direction which is essentially opposite to the opening direction of the flow opening of the arterial lumen. The result of this construction and structural relationship is a minimal risk or likelihood of blood recirculation. The directions and orientations associated with the exemplary embodiment allow the arterial (in-flow) lumen to directly capture blood from the natural flow pattern, rather than sucking the blood around the edges of the catheter. The exemplary embodiment causes less shearing of the red blood cells due to edge-flow patterns and therefore, less hemolysis.